196 GENERAL REVIEW. 



genial bottom-heat of 60 to 70. No hybrids have been raised 

 in gardens, but this might readily be done. Their pollen is in 

 waxy masses, like that of most tropical Orchids, and will be 

 found embedded in radiating slits or cavities of the fleshy 

 column or disc in the centre of the flower. Fertilisation may 

 be easily effected by smearing these glutinous masses on the 

 viscid stigmatic surface, which can be seen through a lens. 

 The drop of nectar or honey secreted on the stigma of 

 Hoya is one of the best of all mediums in which to grow 

 pollen-grains i.e., cause them to emit their fecundating tubes 

 on a slide for microscopic examination ; and this being so, it 

 might be found of great service by hybridisers to quicken the 

 pollen placed on the stigmata of other flowers. In many cases 

 the natural secretion of limpid moisture on the stigma does 

 not seem suited to the requirements of the foreign pollen 

 applied in hybridising; and when this is observed to be the 

 case, it is advisable to remove a drop of the secretion from the 

 stigma or stigmas of the pollen-bearing parent, and place it on 

 the stigmas to which the foreign pollen is to be applied. The 

 mucus of Hoya seems congenial to the growth of nearly all 

 pollen-grains ; but a series of experiments made with the nectar 

 and pollen of different flowers is much wanted, and might 

 throw much light on the subject of hybridisation and cross- 

 breeding. 



Stapelia (Carrion - flowers). This is a singular genus of 

 succulent Cape plants, which numbers nearly a hundred species ; 

 but a very small proportion are now to be found in ordinary 

 gardens. They are branched, leafless plants, which seldom 

 grow under cultivation more than a foot high, and which bear 

 curious stellate, waxy flowers, that vary greatly both as to size 

 and colour. A marked and well-known peculiarity connected 

 with the flowers of these plants is their unpleasant, and in 

 some cases even repulsive, odour. Another marked feature in 

 their economy is their having waxy pollen-masses analogous 

 to those of many Orchidaceous plants. The carrion - scent 

 emitted by the flowers, by attracting flies, is doubtless sub- 

 servient to the process of artificial fertilisation, without which 

 the seeds of these plants could not be produced. It is very 

 common, when these plants are in bloom, to see great blue 

 flies busily engaged in depositing their eggs right down the 

 centre of the flower ; and in doing so, they not unfrequently 

 dislodge the pollen - masses, and thus unconsciously effect 

 fertilisation. It is useless to attempt striking cuttings during 

 the dull autumn or winter months, as the shoots do not then 

 possess vital energy enough to emit roots, but damp off. Some 



